“Green bean” is a generic term used for the skinny, long green beans almost universally available canned, frozen, and fresh. But the world of beans is much wider (and more colorful), as a trip to a farmers’ market will attest.
Green, string, wax, or snap beans: Long and rounded, these are most often bright green but also come in yellow and purple. The fibrous string that was once their trademark has been bred out of them, although you’ll still find it in some heirloom varieties.
Romano beans: Flat and wide, Romanos can be green or yellow. When young and short, they’re tender, but they are often sold larger (as long as 6 inches), with visible bean seeds, at which point they need to be cooked longer.
Spanish Musica beans: Flat, green, and meaty, these look similar to Romanos but have a delicate nutty flavor.
Chinese long beans or yard-long beans: These giants belong to a completely different branch of the bean family. They are the immature pods of a variety of cowpea (an African bean variety that includes the black-eyed pea). These can grow to great lengths but are best between 12 and 18 inches. Similar in flavor to the string bean, these are softer and starchier.
Avoid buying beans that look withered at either end—it means they’ve been sitting a while and are losing moisture.
Green beans need just a quick rinse in a colander. Snap or cut off the stem end, which tends to be tough. (You can cut off the tails as well, although it’s not necessary.) Note that beans react quickly to acidity, losing their bright color when you season them with lemon or vinegar. You can use the following cooking methods for all types of green beans.
Blanch: Immersing beans in a pot of salted water briefly and then removing them to a cold water bath sets their color and brings out their sweetness. We like to do this even if we plan to sauté or stir-fry them, especially with the meatier varieties, as they’ll cook faster. The more delicate, thinner varieties (like haricots verts) need only a quick blanch before being tossed into salads or side dishes.
Steam: Cooking beans in water vapor in a closed vessel is the fastest method and doesn’t leach out flavor or nutrients, as boiling can. Foods steam best in shallow layers, though, so unless you want to work in batches, you’re better off boiling large amounts of beans.
Boil: All these beans taste delicious boiled in salted water until tender and served with butter or olive oil, a squeeze of lemon, and finished with a sprinkle of sea salt. Boiling softens vegetables faster and more thoroughly than steaming, because contact with hot water dissolves and extracts pectin and calcium from the plant’s cells.
Beans relinquish sweetness the longer they’re stored, so try to use them right away. If you can’t, store them in the refrigerator for up to four days in a paper bag or a plastic bag with holes punched in it so the beans can breathe.